Shortwave Therapy

Non Thermal Effects

How does shortwave work non thermal (non-thermal or athermal) in short:

It affects Cells

  • Influencing the function of cell membranes and organelles 
  • Changes in protein conformation
  • Excitation of molecular vibrations
  • Changes to the behavior of cell receptor proteins
    • Foster 2000, Foster & Galser 2007, Rao 2008, Al-Mandeel & Watson 2008, Laurence 2000, Chiabrera 2000, Challis 2005

How to get non thermal effects:

  • Use pulsed shortwave
  • Use fewer pulses
  • Stay below 5w

Theory:

Non thermal effects happen at the cellular level, influencing the function of cell membranes and organelles (Foster 2000, Foster & Galser 2007, Rao 2008, Al-Mandeel & Watson 2008).

This can have a direct effect on inflammation. A characteristic of inflammation is a reduction in the activity of the cell membranes. This altered potential affects ion transport across the membrane, and the resulting ionic imbalance alters cellular osmotic pressures. Shortwave can help restore this balance either a direct ionic transport (as explained earlier in how shortwave works) or by activation of various pumps (sodium/potassium) according to Sanseverion (1980)

Other effects produced by shortwaves in the tissues such as, changes in protein conformation and changes to the behavior of cell receptor proteins are proposed to be behind some of the non-thermal effects (Laurence 2000, Chiabrera 2000, Challis 2005)

Adey (1993) said:

Modulation of cell surface chemical events by weak EM fields indicates a major amplification of initial weak triggers associated with binding of hormones, antibodies, and neurotransmitters to their specific binding sites. Calcium ions play a key role in this amplification.

How does these low level fields create these non thermal responses? By interacting with signaling processes (Luben 1991). 

Tissues have a number of internal processes for signaling and communication between cell types. Hormones and neurotransmitters move from one cell type to another and modulate the metabolic responses of those tissues (a good example would be growth hormone – hGH is released by the pituitary and then interacts with many tissues to create responses like increased muscle and bone growth). Pulsed shortwave has been linked to triggering these responses without the need for the hormone or neurotransmitter to be present (it tricks cells into behaving like they have had the interaction) Luben (1995).

Excitation of molecular vibrations is also proposed as a non thermal effect however, this is potentially a complex issue as increases in molecular vibrations and production of heat are not mutually exclusive.

Debate:

The ‘non thermal’ effects of RF energy are often quoted as the ‘real purpose’ of shortwave machines. Notice the quotes in that sentence? They are there for good reason!

Why?

Lets break down that statement.

‘Non thermal’ effects. Sounds simple but like any topic overly researched the detail can be confused with ‘real world’ applications (more quotes!)

So ‘non thermal’ should be simple lets take it at face value – the mechanism of RF interaction with the tissues not creating heat. 

Can that even be done in the ‘real world’ put simply no:

Why I hear you ask?

Put simply creating a true ‘non thermal’ effect would be impractical and in real patients just wouldn’t work. Lets look at why:

All tissues are complex and diverse – what that means is normal tissue is a mixture of many things most prominently water, fat, skin, muscle, bone, etc. etc. Each of these absorbs any RF at different rates know by several names but the main one used is the specific absorption rate (SAR). 

In the ‘real world’ what this means is when you apply a certain amount of RF to living tissue something will react by getting hotter or warming up. That means that tissue has now had a thermal effect and will have a thermal effect on tissues around it through simple conduction. This heat may even be ‘imperceptible’ meaning the patient and/or the therapist can’t feel any.

So ‘non thermal’ becomes a ‘race to the bottom’ in other words how little RF can be applied so nothing heats up. Obviously this does not work in patients. A simple example would be a problem in the patella tendon. A dose giving real non thermal effects to the ligament will heat the skin and the synovial fluid around the ligament.

So the argument about the detail starts.

Here is where terms like ‘microthermal’ or ‘quasithermal’ (low levels of thermal changes in tissues) come from.

RF treatment for ‘non thermal’ effects then might produce some warmth in the tissues around where you are treating but could still be considered to be ‘non thermal’ in the tissue you are treating. Keep in mind that patients can have trouble perceiving heat at depth due to the lack of thermorecptors. 

So how high can you go?

It has been said that treatments below 5w are non thermal.

So can you just set the parameters on the machine how you like and just make sure you are under 5w (e.g. frequency, intensity, duration etc.)

Well no. Generally it is accepted that pulsed short wave is more likely to produce biological effects than continuous wave at the same power (Postow & Swicord (1996), Adair & Black (2003)).